Gasoline Direct Injection (GDI) engines are a special breed in that the intake valves never have any fuel sprayed onto them. The injectors, under high pressure, direct inject fuel into each cylinder while the engine is running. However, these engines do have PCV and EGR systems and as a result, many GDI engines have been suffering from issues related to carbon build up in the intake manifold and especially on the backs of the intake valves and the valve stems. In turn this reduces air flow into the engine, with the resulting loss in power, loss in fuel economy and rough idle.
One way that the manufacturers and the aftermarket is trying to deal with this issue is by using a “catch can” and/or a “heated PCV” to reduce the flow of oil droplets into the intake from the PCV system. However, it seems that in many cases, these precautions either don’t work or don’t work very well. Audi, VW and Porsche appear to be having major issues with carbon build-up on the valves in many of their newer GDI engine designs. For the most part, the accepted “cure” is to pull the intake manifold, and using a combination of scraping and solvents, to manually clean the valves and stems.
If one were to inject MMO into the intake manifold on a GDI engine by using something like an Ampco top end oiler unit, would the MMO be effective at dissolving existing prior carbon build up on the valves (keep in mind this is a different use than in older carb or even newer fuel injected engines due to the change in the flow of fuel)?
Similarly, would there be any risk that MMO could make the situation worse and actually begin to form its own layer of carbon on the valves given that there is no fuel passing over the valves to help clean them and wash away the MMO (keep in mind that auto engineers are trying to eliminate the introduction of particulate oil into the intake manifold to solve the carbon build up issue)?
An additional related question is at what temperature does MMO boil off and turn to carbon? If intake valves run at 300+ degrees would that be a risk factor for MMO worsening the carbon buildup on the valves?
I would very much appreciate a fact based answer from the MMO team in regard to these questions.